From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 545E5C433FE for ; Wed, 19 Jan 2022 18:02:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=czio5MQ1S8+7HR9QWQSlBxWzEfdzrxRjKKfNn+Y3QhA=; b=2Qob8GNY7CbRwu z0qPLkpgl9ostsiVYwOglWBPXEDdBTLC924fsoDPRCRbZ3vIY6Tu8PrSOiozNmIeSQBrAojhU1JXv ZBIIQkx66cvXqi/4tjLAs1JbE+8UF72d/uGcj+ilK2dYn1P/Ust26K410wDs5wru6inZ55GSz0hsY zjMHa7472JSAFa+CiVek8IclcFloNsQ5ZCmtMtRl59L/1H7sWsROiRSDf4l1dQUAuwLCjgqgEk10p +u1GGJA0UCwsP7caKu7wk7g+IypfnjlBrEH9ZE3+gedRdzAqrjOcCUefXOfEJH9mhxEdmF71K3Hi5 cEYupajalIE1dkdjngAA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nAFH1-006hCO-4p; Wed, 19 Jan 2022 18:01:31 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nAFGz-006hCA-M1 for linux-arm-kernel@bombadil.infradead.org; Wed, 19 Jan 2022 18:01:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=wl35Nv5bzMCc708L4TqlyxLqxeH3mVDxX3k5zPuEGYo=; b=e6nKWnC2p+Tf/OuPB41XZewJTw 9aR5M2y6V/hfTahSIhFlgmKQoZ3OddEQoQb9TKA0jXQ2gbJRF6D0r6+TfbLm/heQJSprsV/QYpqcY qq11o1p/4VBTmIwr4vC84NqqRk0geKSmNkyOUY69cPTWm88tcFDEhTdqyUm7MD1Lbct50fNlKC99a BsyYPEPzDplXfd6VxNXD1dTJDfwfytPkKD8GZO/CVy0HjvUTo6ESV0VgcPXaG/+fAuvU5U+FtEZze H0KgRLdO8+qm8+U5XG8DSeVKCdBYV9XUUZv9SK820h3R+8x+V0sT9bzgLLNLmFZSPNdd5Lmkzn0+L h7HcSL4g==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nAFGu-00BeGf-9X; Wed, 19 Jan 2022 18:01:24 +0000 Date: Wed, 19 Jan 2022 18:01:24 +0000 From: Matthew Wilcox To: "Russell King (Oracle)" Cc: Robin Murphy , Yury Norov , Catalin Marinas , Will Deacon , Andrew Morton , Nicholas Piggin , Ding Tianhong , Anshuman Khandual , Alexey Klimov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] vmap(): don't allow invalid pages Message-ID: References: <20220118235244.540103-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jan 19, 2022 at 05:54:15PM +0000, Russell King (Oracle) wrote: > On Wed, Jan 19, 2022 at 04:27:32PM +0000, Matthew Wilcox wrote: > > On Wed, Jan 19, 2022 at 01:28:14PM +0000, Robin Murphy wrote: > > > > + if (WARN_ON(!pfn_valid(page_to_pfn(page)))) > > > > > > Is it page_to_pfn() guaranteed to work without blowing up if page is invalid > > > in the first place? Looking at the CONFIG_SPARSEMEM case I'm not sure that's > > > true... > > > > Even if it does blow up, at least it's blowing up here where someone > > can start to debug it, rather than blowing up on first access, where > > we no longer have the invlid struct page pointer. > > > > I don't think we have a 'page_valid' function which will tell us whether > > a random pointer is actually a struct page or not. > > Isn't it supposed to be: > > if (!pfn_valid(pfn)) { > handle invalid pfn; > } > > page = pfn_to_page(pfn); > > Anything else - even trying to convert an invalid page back to a pfn, > could well be unreliable (sparsemem or discontigmem). This function is passed an array of pages. We have no way of doing what you propose. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel